Math question: Find the derivative of f(x) = sin(x)cos(x) + tan(x)sec(x).
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Math question: In triangle ABC, angle A is 60 degrees, angle B is 75 degrees, and side AB is congruent to side BC. Determine if triangle ABC is an isosceles triangle.
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What is the value of f(x) when f(x) = c, for any given interval?